With a referendum due to take place alongside the Northern Ireland Assembly election on 5 May, both the main nationalist parties and Alliance have declared their support for the Alternative Vote system.

However, the two main unionist parties and the Traditional Unionists want to keep the current first-past-the-post system for Westminster elections, while the local Green Party would prefer a proportional representation system.

Holding this referendum was one of Nick Clegg's demands before he agreed to go into government with David Cameron's Conservative Party.

The Liberal Democrat leader has long believed that the current Westminster voting system is unfair, while the Conservative leader disagrees.

As things stand, MPs are elected according to the first-past-the-post system. It's simple: a voter puts an X against the candidate they back and whoever gets the most votes gets elected.

Preferences

Under the Alternative Vote, an MP would have to get more than 50% of all the votes cast.

Instead of an X you'd write in one, two, three and so on.

Less popular candidates would be eliminated and voters' second and third preferences would help a candidate climb past the winning halfway point.

Pat Doherty of Sinn Fein said his party was backing the Alternative Vote because it is an improvement on first-past-the-post.

"It isn't full PR in the sense of multi-seat constituencies, so in our dialogue around this we've accepted it is an advance and will be in favour of a 'yes' vote," he said.

The SDLP's Conall McDevitt said: "AV is a good idea because we don't want any more Westminster elections here fought as if they were sectarian headcounts."

But both main unionist parties prefer to retain the Westminster system as it is.

Nigel Dodds of the DUP said: "It has been done as a miserable compromise as Nick Clegg even called it, to help the Lib Dems and it won't improve the electoral system or parliamentary representation one iota."

The UUP's Fred Cobain said: "We're against it because we think the system we have produces stable government."

If you're not that excited about the referendum, then don't worry, you're not alone. When the No to AV group hired the Ulster Hall for a rally last month only seven people showed up.

Campaigners on both sides will be hoping the interest picks up in the weeks running up to the referendum.